Interpretive Summary: In many areas, septic tank systems with field lines are commonly utilized to treat wastewater discharges from households or other sources. These septic systems usually fail when soil percolation rates are inadequate for the system to work properly. Constructed wetlands have been used in residential areas where the septic systems failed. Research reports also indicate that a subsurface or surface flow constructed wetland can provide further treatment of the effluent with minimal cost and maintenance. Constructed wetlands mimic natural wetlands and are designed to treat municipal, agricultural and industrial wastewater from point and non-point sources. As wastewater flow through the system, suspended solids, nutrients, and organic materials are filtered, absorbed, or degraded by plants and microorganisms living in wetland. The objective of this study was to evaluate the capability of residential constructed wetlands for improving the water quality of wastewater being discharged from a septic system. The results indicated that constructed wetlands are very effective in the treatment of septic tank effluent. Most of the contaminants including organic and inorganic compounds and microorganisms were greatly reduced from influent to effluent points. In general, constructed wetland technology can be used as an effective on-site wastewater treatment method, particularly in rural areas.

Technical Abstract:
Constructed wetlands mimic natural wetlands and are designed to treat municipal, agricultural and industrial wastewater from point and non-point sources. In many areas, septic tank systems with field lines are commonly utilized to treat wastewater discharges from households or other sources. These septic systems usually fail when soil percolation rates are inadequate for field lines to work properly. Constructed wetland can provide further treatment of the effluent in these situations with minimal cost and maintenance. The objective of this study was to investigate the wastewater treatment efficacy and water quality improvement by six residential constructed wetland systems. Water samples were collected monthly for one year from inlet and outlet points of each cell within each system and analyzed for the following water quality parameters: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), phosphorus (P), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total ahl nitrogen (TKN), and fecal coliform bacteria FC). All the parameters analyzed were greatly reduced from influent to effluent points. The BOD5 was reduced up to 85%, while FC bacteria reduction was as high as 99% at most of the sites. There was significant reduction in TSS (88%), TKN (74%), P (80%), and NH4-N (56%) in most of the constructed wetlands. Data also showed that treatment of septic tank effluent continued during four seasons.